Effect of Grouting Concretion on Groundwater Environment in Goaf

Ning Jiang, Yin Liu, Jinhai Zhao, Yun Dong, Changxiang Wang

Abstract


Fly ash and cement are widely used as filling materials in coal mine backfill mining ofChina, but there are few researches on the influence of various kinds of fillings composition in mining area environment. In order to study the influence of the grouting concretion on groundwater environment, the static leaching method is used to soak the cement-fly ash concretion. The PH value of the leaching solution and the fluoride ion, total hardness and heavy metal content in the leaching solution were tested by using direct potential method, EDTA titration, ion selective electrode method and inductively coupled plasma spectroscopy respectively. This thesis uses “F” value method to explore the relations between cement-fly ash slurry concretion on the groundwater quality. The experimental results showed as: First, fluoride ion concentration in the leaching solution was maintained at 0.85 mg/L; Second, the total hardness of the solution was increased by 420 mg/L at 28d, close to the groundwater quality standard of class II. Then the total hardness of the solution was declining, which was lower than the groundwater quality standard of class II standard. The peak value of zinc ions in 28-47d reached 0.08mg/L, close to the groundwater quality standard of class II, then gradually decreased, which was lower than the groundwater quality standard of class II. When metal lead ion reached 0.4mg/L at 28d, it would meet the groundwater quality standard of class II which would not pollute the groundwater. However, the PH value of leaching solution reached 11 at 10-15d, and the PH value at 10. The water quality remained above the “good” level after 28d by using the “F” value method. Integrated analysis implied that the cement-fly ash concretion had a great impact on the change of the water quality in a short time, but the long-term effect was mainly reflected in the influence of the PH value of groundwater. The significance of this thesis can provide a suggestion for the influence mechanism and process of cement-fly ash cementing material on water quality and its long term influence on groundwater quality.


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